1,2,3-Triazoles, Regitz diazo reactions

Theis, W, and Regitz, M., Investigations on diazo compounds and azides. Part 60. Reactions of 3H-l,2,4-triazole-3,5(4//)-diones with vinyl diazo compounds, Chem. Ber, 118, 3396, 1985. 

The Regitz reaction provides a gateway for the synthesis of the following diazo derivatives cyclopentadienes, cyclohexadienes, ketones, 1,2-, and 1,3-diketones and their derivatives, (3-keto esters, a-iminoketones, a-ketohydrazones, amino-1,3-diketones, nitro-1,3-diketones and 1,3,5-triketones. Secondary reactions of diazo compounds lead to heterocycles such as 1,3,5-triazoles, 1,2,3-thiadiiazoles, and pyrazolines. 

For acceptor-substituted alkynes, it is possible to use trimethylsilyl azide as transfer reagent (cyanogen azide does not react). The reaction (2-90) is not regiospecific, but the silylated triazoles 2.225 can be hydrolyzed and deprotonated to the anion 2.226. The latter reacts regiospecifically with cyanogen bromide to form the triazole-carbonitrile 2.227, which is in equilibrium with the a-diazo-A -cy-ano-imine 2.228 (Regitz et al., 1981 b). 

P-Enamino ketones or esters 30, readily accessible from 1,3-diketones or P-ketoesters, are susceptible to diazo transfer (Regitz reaction [499]) with mesyl or tosyl azide in basic medium at room temperature and subsequent cyclization to give 4-acyl-(or 4-carbalkoxy-) 1,5-substituted 1,2,3-triazoles 32 [500] ... 

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